The effect of maternal cigarette smoking during pregnancy on fetal growth and survival are profound. Relationships to subsequent child development are problematical. Some past studies have found strong association, others only weak ones. These studies have been plagued by unrepresentive populations, small numbers or weak design and analysis, or combinations of these flaws. We aim to study this issue in a large, representive population (all 17,000 children born in Britain during one week in 1970) already assessed at birth and age 5 and to be studied as well at age 10. By use of longitudinal assessment, we can test for differences in social drift between smokers, ex-smokers and non-smokers over time, and with extensive cross sectional social data, can test whether stratification by social class based on husbands' occupation only partially controlled for real social difference. In addition, we will study whether maternal smoking was associated with difference in the quantity and quality of preschool educational provision. If differences in child developmental indices are associated with maternal smoking, we will test whether they are indirectly, and therefore more likely to be non-causally, related. The outcome measures include somatic growth, and measures of both mental ability and achievement. The entire cohort was assessed at birth and age 5. This proposal is to support analysis of that data, as well as to supplement the subsample who are to be seen at age 10 (1000 handicapped and 400 randomly selected control children) with 1000 additional non-handicapped children, stratified on mothers' social class and smoking habits during pregnancy.